Thermal latch circuit breaker with screw adjustment for latches



May 19, 1953 R. c. INGWERSEN THERMAL LATCH CIRCUIT BREAKER WITH SCREW ADJUSTMENT FOR LATCHES 2 Sheets-Sheet 1 Filed Feb. 7, 19'52 INVENTOR RICHARD C- INGWERSEN BY%Q/F/ZMM I ATTORNEY y 1953 R. c. INGWERSEN 2,639,349

THERMAL LATCH CIRCUIT BREAKER WITH SCREW ADJUSTMENT FOR LATCHES Filed Feb. 7, 1952 2 Sheets-Sheet 2 Fig- H.

INVENTOR RICHARD C \NGWERSEN BY z m ATTORNEY Patented May 19, 1953 THERMAL LATCH CIRCUIT BREAKER WITH SCREW ADJUSTMENT FOR LATCHES Richard C. Ingwersen, Jackson, Mich., assignor to Mechanical Products, Inc., Jackson, Mich., a corporation of Michigan Application February 7, 1952, Serial No. 270,335

This invention relates to improvements in electric switches which employ overload protection and of the kind, as disclosed in the prior patents in my name, No. 2,485,736 patented October 25, 1949, No. 2,513,564 patented July 5, 1950, and No. 2,514,545 patented July 11, 1950, in which a bimetallic thermal element connected in electrical series with a movable contact assembly is employed, in association with an actuator re-set plunger button and abutment assembly, to form a latch which, by engagement with the abutment, holds the movable contact assembly in closed position but is subjected to the heat of the current flow to disengage the abutment automatically upon the occurrence of a predetermined current overload and thereby release the movable contact assembly to move to open position.

It is an object of the present invention to improve these prior art electric circuit breakers by providing a simple and inexpensive. yet reliable, means for adjusting the thermal element while in-situ in the circuit breaker casing, having regard to the degree of engagement of the thermal latch with the abutment, whereby the operation of the thermal latch can be finally set to suit the particular overload current rating involved. In this respect, the construction of the thermal element itself permits fine calibration as to particular current ratings, which, however, the present invention augments by providing for final adjustment of the degree of contact of the thermal latch element with its abutment, and by enabling this to be done when the circuit breaker has been subjected to laboratory test prior to distribution.

It is a further object of the invention to provide an improved mode of assembling the parts which go to make up the actuator plunger and button assembly, which greatly simplifies the assembling operation compared with the prior art constructions.

These and other objects and advantages of the invention, residing in the construction, arrangement and combination of parts, will appear clear from a consideration of the following description with reference to the accompanying drawings and from the appended claims.

In the drawings:

Fig. I is a view of a circuit breaker in accordance with the present invention, showing 111 side elevation the improved actuator plunger and button assembly, with one half of the casing removed,

Fig. II is a part sectional end view of Fig. I

7 Claims. (Cl. 200116) showing the actuator plunger and the cross screw for adjusting the thermal latch element, as well as the opening in one side wall of the casing through which access is possible to adjust the cross screw, and

Figs. III and IV are similar views to Figs. I and II, respectively, but of a modified construction according to the invention.

In the drawings, wherein like parts have been given the same reference numerals, a circuit breaker is shown having the same general features of construction and operation as disclosed in the prior Patent No. 2,485,736.

The movable contacts II) are carried upon arms [2 secured upon a central thermal latch and guide finger assembly mounted for rectilinear and guided sliding movement with respect to a hollow block I4 of insulating material. This block I4 is connected with two further blocks [8 and 20 of insulating material. These blocks, which form the re-set actuator plunger, indicated generally at l6, are secured together in axial adjacent relationship by a central tie screw 22.

The block members [4, l8 and 20 are formed with central bores through which the tie screw 22 is capable of being passed. The head 24 of the screw is held against an annular ledge 26 formed in the block member I4, when the screw threaded portion 28 is screwed into a screw threaded boss portion 30 of the block member 20. Ihe block 20 is shaped at its outer end to form a push button accessible by the operator from outside the casing for resetting the thermal latch and guide finger assembly after the same 'has been released from its normal set position within the casing upon the occurrence of a predetermined current overload conducted to the thermal latch via the contacts I!) and arms I2. This block 20 is slidably mounted within a further block structure 2| of insulating material fixedly mounted in the casing section 23, the casing being composed of two similar sections of insulating material secured together by transverse screws, indicated at 25.

The bimetallic thermal latch assembly is indicated generally at 32. It has one side 44 of U-shape in electrical series connection with the movable contacts I0 and engageable with an abutment 34 on the fixed block part 2| for holding the latch in the set and latched position, with the movable contacts I0 closed upon their companion fixed contacts 36 against the action of the coil springs 38, which are stressed when the thermal latch is engaged with the abutment, as

disclosed in the said prior patents. The springs 38 are connected between the unit assembly, constituted by the connected arms l2 and thermal latch assembly 32, and arms 3! integral with the fixed block 2|.

In the constructions illustrated, the thermal l tch has only one sided latc ing n agemen with theabutment, the'other side t being formed to have sliding engagement against the side surface 42 of an integral part of the block 2|.

In both forms of the invention. p lqvisionis made to adjust the position of the thermal} latch part M with respect to the abutment ledge 34.

Such adjustment involves? varying. within fine-- limits, the extent or distancetheedge'of'the-latch part M engages the abutment ledge 3 inwardly:

from the release side of this ledge, that. the side from which the thermal latch disengages under overload. Such adjustment is rendered possible in each case by a screw 46 which is scr wed into a cross ore 8 i the block. part i M. which: crossbore: extends through the" tie; screw 22;;whereby; the adjustment screw 46 forms; the dual. purpose of an adjustment screw to adjust the thermal latch part i t and a look for the tierscrew 22 in Figs. I and II the adjustment S IF WM is set at an inclination whereasin Figs. III and IV itextends horizontally. In either case, the head 5.9 of the adjustment screw is exposed to=oneside of thet-hermal latch assembly whileits opposite and extendsthrough the opposite side of the block Hi and lies against the inside of the thermal latch part fit: Thuaby adjustment'of the-screw as by a screwdriver,- it is, readily-possibleto make, the; screw bear: againstthethermal latch part itto a great'en or less extent and thereby vary the position of the-latch-edge upon the abutm at ledge, Accessto the screw headed is possible through an opening 52?- in the corre- 4- sponding casing-side wall 54.. This openingis; so disposed as; to lac-opposite the screwheadrfiil when the thermal latch assembly. is inthe extended position as shown in the drawings. Prior to-final laboratory testing: of a circuit breaker incorporating this: screwadl'ustment. feature the; opening: 52- will be left open'so: that" any adjustment decided as necessary astheresult of test can be readily made; Thereafter't-heopening is closed orsealed. Thi'smaybe-accomplished by screw"- ing' a. stud 56' into the openingfiii; the opening bBlI'lgSGITQWJ threaded to receive thestud;

- Having thus described this invention what-I claim novel and wish to secure by Letters Patent is as-ifcllews: I

1'. In an electric switch. having overload protection; casing structure presenting-- a. side-wall with an opening tli'erethrough; an actuator plungerreciprocablymounted in said casing and carryinga thermal latch element, said casin structure includingflxed abutment structure for engagement by saidthermallatchelement to hold the element in. latched position, andascrew memberon-said-actuator plunger and engageable with said thermal latchelement to adjust the position thereof with respect to said abutment structure, said casing opening being so positioned that the said screw member is accessible for adjustment when the said thermal latch element is latched against said abutment structure.

2. An electric switch as claimed in claim 1, said actuator plunger being built-sup from separate parts, a tie screw extending through said parts and holding them secured together in assembled relation, said screw member passing through said tie, screw to. lock the, screw in position as well as topermitadjustment of said thermal latch element.

3.1man electrieswitch having overload protection; casing structure, fixed and companion movable contact'ineans in said casing structure, anv actuator plunger mounted in said casing structure, said plunger carrying a thermal element in electrical series connection with said movable contact means,..and combined therewith to fcrmraxslidable unit; said casing including abutment structure engageable by thermal element: tohold. the movable contact means closed, sprin means connected with said slidafcle unit andsnfessed'whcn said-thermal element is engaged with saidabutment structure; said slidahjle unitacarryins:adjustment means engageaole with said thermal. element to vary the'pcsiticn-of engagement of the element With-theabutnent structure;

4:. Ari-electric switch asclaimed in claim 3; s aid casing structure including a side wall. with an opening, said adiustment means being accessible for" adjustment through said opening when the thermal element is engaged with: said; ahjut merit structure.-

-An elec'tric-switch as claimedinclaim' 3; said actuator plunger being composed of separate in axial assembly, a longitudinal tie screw extending through saidpartsand securing them together in said assembly, said-adjustmentmeans comprisinga screw member, said screw member extending crosswise through said tie screw in lockingrelation-thereto;

Anaotuator assembly foruse in an electric circuit breaker of the kind described, said assemr bly comprising separate plunger bodyparts, a longitudinal tiescrew extending. within. and th ough said. parts and. securing them. together in assembly to-fonnaplunger, abinietallic thermal means mounted on said plunger and imeluding a. fiexible blade; and a screw elementon Said plunger and engageable. with said. blade to efiectadjustmentthereof in. a lateral direction.

'75 An actuator assembly asclaimedinclaim 6, said screw element extending crosswise. through said longitudinalrtiescrew in lock ngrelationship with respect thereto, said screw element being adjustable axially. to efiect said adjustment of saidblade;

RICHARD (1.. INGWERSEN.

No references. cited. 

